Intelligence and Miscellaneous Articles. 207 



add that we may anticipate the publicatioa of Ni'. Nagaoka's 

 further work in the Journal of the College of Science, Imperial 

 University, Japan, in the near future. 



I am, Sir, 



Yours faithfully, 

 Glasgow University Jan. 21, 1889. Aikitu Tanakadat^. 



ON THE ALTERATION OF THE CONSTANT OF ELASTICITY OF 

 METALS BY THE ELECTRICAL CURRENT. BY C, A. MEBIUS. 



From his investigations on the elasticity of metals, Wertheim 

 concluded that an electrical current, which traverses a metal wire, 

 diminishes the coefficient of elasticity. The determinations of 

 Wertheim are not very trustworthy, and from recent experiments 

 Streintz has questioned the conclusions at which Wertheim arrived. 



Mebius has again taken up the question and attempted to solve 

 it by experiments on flexure. The materials under investigation 

 (two rods of steel and two of iron, two tubes of brass, one silver 

 wire) were laid on two parallel horizontal knife-edges, and the 

 centre was loaded. By means of a microscope with micrometer in 

 the eyepiece, an index could be sighted. The author could not 

 observe any direct action of the current on the bending. Prom a 

 discussion of the results of the observations, it follows that in four 

 experiments, if there had been any alteration of the coefficient of 

 elasticity, it would have amounted to less than 0*089, 0-015, 0*047, 

 and 0'037 per cent, of its entire amount, and accordingly, in agree- 

 ment with Streintz, he assumes that the electrical current has no 

 action on the elasticity. — (Efvers. af h. Vet.-Ahad. Forhandl. 1887, 

 p. 681 ; BeiUdtter der Phys'il; vol. xii. p. 678 (1888). 



ON AN ELECTROMETER WITH A QUARTZ DOUBLE PLATE. 

 BY M. JACQUES AND P. CURIE. 



Two rectangular plates are cut at right angles to the axis so that 

 their long sides are simultaneously at right angles to the optical 

 and electrical axis. The plates are very thin, cut to a few hun- 

 dredths of a millimetre, and are then cemented to each other, so 

 that the electrical axes in them are reversed. The two external 

 faces are silvered, and freed from the silvering on a narrow edge. 

 If the silver coatings are brought to a difference of potential, the 

 plate curves, as can be seeu at a glass index placed at the free end 

 of the plate. At its end a small photographed micrometer is 

 fastened and is viewed by a microscope. 



If A:=6-32xl0"^ the deflexion 6 of the end of the needle 

 =^lc(L/ef . (2\ + L)/L .Y in absolute electrosfatic measure (C.G.S.), 

 where L = the length of the quartz plate, e the thickness, X the 

 length of the needle, V the difference in potential in absolute 

 measure (that is, a unit equals 290 volts). 



The instrument is aperiodic, but not very sensitive, and can 

 hence be used for higher potentials, that is from about 0*5 to 

 several thousand volts. — Comptes Eendus, p. 1287 (1888); Bei- 

 hldtter der Physik, vol. xii. p. 687. 



